Drive suitable for remote control



E. B. HANSELL Aug. 31, 1937.

DRIVE SUITABLE FOR REMOTE CONTROL Filed Oct. 25, 1934 ATTORNEY PatentedAug. 31, 1937 UNITED STATES PATENT OFFICE DRIVE SUITABLE FOR REMOTECONTROL Erik B. Hansell, New York, N. Y.

Application October 25, 1934, Serial No. 749,963

4 Claims.

This invention relates to drives suitable for remote control, and isherein illustrated as embodied in a radio receiving device.

It is often desirable to move to variable amount a control or otherdevice at a distance and many mechanisms have been designed to that end,but it has been found diflicult to devise mechanism which can be easilyattached to a standard article, like a radio set, and be entrusted tounskilled hands for installing it. If a control for a radio set, forexample, is to be installed on one floor of a house for controlling thetuning of the set on another floor, the connections must be electricalto avoid the otherwise inevitable lost motion, and the length of theelectrical connections introduces a complexity by reason of theelectrical resistance which varies with their length.

If relays are introduced into the set, the complexities are added to,and parts are introduced which are likely to be damaged by roughhandling in shipping. Moreover relays usually involve contacts which maybecome dusty and thereby of uncertain electrical efliciency. Moreover;the use of relays usually involves either timed mechanical drives orseparate electric conductors for each portion of the tuned device.

Similar difllculties arise in other kinds of devices in which it isdesired to drive some distant device, or part, to an accuratelycontrolled variable extent.

According to the present invention these and other difficulties anddisadvantages are overcome, and an electrical device is provided whichrequires a very small current, is capable of being carried oninconspicuous wires, and yet which easily and almost positively controlsa device using almost any amount of power, at least any power capable ofbeing furnished by a power electronic vacuum tube.

In the form of the device disclosed herein in some detail one side of aWheatstone bridge contains a settable variable resistor and the otherside contains a second variable resistor, which, in reality, serves asan indicator for the controlled device, herein shown as the radio tuningcondenser.

These resistors are shown as balanced around the grid of an electronicvacuum tube, so that the tube may, through its plate control the grid ofa second or power tube forming part of a circuit adapted to drive thearmature of a motor in one direction.

The plate of the second tube is shown in turn as connected to the gridof a third tube, likewise a. power tube, forming part of a circuitadapted to drive the motor armature in the opposite direction.

These connections are shown as such that the armature is turned by thecurrent from one tube only part of a turn under the torque of thecurrent driving it and then is arrested by the current from the otherpower tube. In the structure shown, this result is attained by directlycoupling the motor shaft both to the shaft of second resistor and to theshaft of the variable tuning condenser.

In the structure shown, it has been found possible to obtainsatisfactory tuning by a tuning dial at a resistor connected to theradio set by upwards of fifty feet of No. 38 cotton covered copper wire,and to use a rotary motor armature specially wound with No. 44 enameledcopper 'wire, with the result that a current of a few milliamperesoperated the shaft of the tuning condenser.

The device is shown as adapted to use alternating current, but with somemodification, mainly simplification, it may be adapted to use directcurrent.

The device is shown as forming part of a radio receiving set, and, tomake it almost fool-proof for radio users, is shown with a push buttonstarting device which, for some uses will prove unnecessary. Moreoverthe tuning knob and the resistor it controls are primarily adapted forradio use, while for other uses the resistor may take other forms, such,for example as a lightsensitive electron tube which, of course, requiresno knob.

Even in radio sets a single tuning handle will often be all that isdesired, and, as will appear, certain parts will then be unnecessary.

It will be noted that one variable arm of the Wheatstone bridge startsthe motor and, in effect, the other variable arm stops it. It will benoted that the device requires no making and breaking of heavy currentsthrough relays, thus making the device fool-proof in the sense that anordinary radio set is fool proof.

Other features and advantages will hereinafter 45 appear.

The accompanying electrical diagram shows one form of the invention.

In the accompanying diagram showing the in vention as embodied in afamiliar type of radio receiving set, the radio set may be tuned fromany position of the parts by first pressing a push button,diagrammatically shown at I 0, so as to warm up two power electronvacuum tubes l l and I2, and incidentally vwarming other tubes describedbelow. v

The current for warming the tubes comes from a power source shown as twoleads 8 and 9 carrying a house alternating current. When the button I ispressed it closes a circuit through a conductor I5 connected to thetuning lead wire l6 connected to an arm |1 fastened to a motor armatureshaft l9 butelectrically insulated from it. The arm l1 when dead liesagainst an arm l8 and closes a circuit from the priming transformerthrough wires 2| and 22. At the same time another arm 23, likewise faston the shaft I9, but insulated from it, and lying on the spring drawnswinging arm 24 completes the circuit through a wire 25 connected to asolenoid 26 forming part of a relay 21. The circuit is thus closedthrough the other wire 28 of the tuning lead.

The circuit closed by the relay 21 is taken from the power source wires6 and 9 being shown as two leads 29 and 30 put into the circuit betweenthe lead 8 and its transformer winding 3|.

As soon as the circuit is closed, tube I2 is warmed by the currentexcited in conductors l3 and I4 excited by the transformer 3| and thetube causes a current to flow through the armature 32 on the shaft l9and turn it to lift the arms l1 and 23 from their terminals l8 and 24.

This current starts because the warm cathode I 33 of the tube l2, heatedby usual heater filament 34, sends electrons to the usual plate 35,closing the circuit from the lead 36, connected to one brush 31 of thearmature 32. The other side of the circuit, connected to the plate 35,consists of a lead 38 coming from the secondary winding 39 of thetransformer 3|. An intermediate point of the secondary 39 is connectedto the other brush 40 of the armature 32 by conductor 4|.

The turning of the armature 32 permanently closes the circuit throughthe leads 29 and 36 by allowing the spring 42 to draw the arm 24 againstthe end 43 of the lead 29.

To tune the radio set there is shown a usual type of variable capacity44 fast to an extension of the shaft I9 of the armature. To turn thiscapacity 44 to vary it there are shown tuning knobs 45 and 46. To effecttuning the operator presses the knob 45 against the tension of a spring46 so as to carry the end of a stub shaft 41 against a terminal 48 ofthe conductor l5 which, it will be remembered, is connected to thetuning lead wire l6.

If the knob45 is then turned it carries a wiper arm 49 across aresistance 50 to vary the resistance. A carbon resistance of half amillion ohms has been found satisfactory. The wiper arm 49 moving on theresistance therefore varies the amount of current which flows through itby way of conductor |5 from the tuning conductor l6 to the tuningconductor 28, the conductors l6 i the two variable resistances 56 and 53to maintain the same voltage on the grid 5|.

If the current through the variable resistance 50 tends to set up ahigher voltage on the grid 5| than the voltage set up by the variableresistance 53, the hot cathode 55 of the tube 52 sends more of itselectrons to the plate 56, increasing the current going through theplate 56 and through a conductor 51 connected to the grid 58 of thepower tube H. The current is able to go through the plate 56 because theconductor 51 is connected by a high resistance 59 to the plus side 60 ofa continuous current source shown as a rectifier 6| taking current offthe transformer 3|. Four million ohms has been found satisfactory forthe resistance 59.

The current through the conductor 51 lowers the voltage in the grid 58compared to the cathode 62 of the tube l, making it more negative inamount suificient to stop the flow of electrons from the cathode to theplate 63, and making the power tube inert compared to the power tube l2.

The connections are such that, at this time, the plate 63 through aconductor 64 changes the voltage on the grid 65 of the tube |2 so as tofacilitate flow of electrons from the cathode 33' to the plate 35. Thisflow constitutes a current through the tube l2 and, consequently,through the conductor 36 and through the armature 32 on the shaft l9.The shaft turns.

If the knob 45 had been turned the opposite direction, the charge on thegrid 58 would have been lowered or-made more to the positive, thepotential would have risen on the plate 63, raising the potential on thegrid 65 to stop the current from the plate 35. At the same time theincreased potential on the plate 63 would cause a current to flowthrough conductor 64, resistance 11, conductor 36, armature of the motor32, and back through conductor 4|, etc. to cathode 62, driving the motorin the reverse direction.

But in other words, when current from preceding tube 52 is of suchmagnitude that the potential across grid resistor 59 of tube raises thegrid 58 (negatively with respect to cathode 62) beyond out ofi bias nocurrent flows in tube II. By the same analysis, since tube H is now thepreceding tube to 2 and it has no current flow, there will be no dropacross grid resistor 11 and consequently grid 65 of tube 2 is at samepotential level as its cathode, and therefore normal plate current flowsin this tube. The reverse action takes place when there is no currentfrom the preceding tube 52.

The turning of the shaft l9 turns the variable capacity 44 and with itthe wiper arm 53a, changing the resistance 53 until it tends to producethe same change in voltage at the grid 5| as the variable resistance 56changed the voltage.

The two variable resistances 56 and 53 are balanced around the grid 5|like two arms of a Wheatstone bridge. The other two arms of the bridgeare shown as two, usually, fixed resistances 66 and 61 connected onopposite sides of the cathode 55 by a conductor 68. These have beenfound satisfactory when approximately about 5000 ohms apiece, but if itis found advantageous to use difi'erent types of resistances forvariable resistances 50 and 53, the resistances 66 and 61 must beappropriately chosen. The variable resistance 53 is shown as connectedby a conductor 69 through a protective resistance 16, advantageously10,000 ohms, to the flxed resistance 61 to complete its arm of thebridge.

The variable resistance 50 is shown as connected by a conductor 1|,through the conductor 28 and a resistance 12, usually like *theresistance 19, to the fixed resistance 66, to complete the other arm ofthe bridge. The resistances 66 and 61 are connected across the output ofthe rectifier 6i through the conductor 68 and the resistances l5 and 16.

The tube 52 is shown as having an additional suppressor grid I3connected to the cathode 55, and with a space charge or screen grid 14connected to its appropriate voltage about 100 volts higher than thecathode, taken between resistance I5 and 16 to the conductor 68. Thesetwo grids increase the sensitivity of the tube 52.

To obtain the needed drop between the cathode 33 of tube I2 and grid 65ahigh resistance ll is shown between the conductor 64 and the conductor36. It has been found possible to use 1500 ohms for this resistance andthis is shown as balanced by 1500 ohms resistance at 18 in the 20conductor 38.

To enable several turning knobs 45 and 46 to be used independently it isneedful to add a stopping electron vacuum tube 19 shown as connectedacross the limiting resistance .16, through which flows a currentdepending on the setting of the variable resistors 50 and 53, thusputting cathode 80-of that tube I9, connected near the variableresistance 53', at one voltage and the grid 8| of the tube at anotherand lower voltage, be-

cause the grid is connected to the transformer side of the resistance18. This difference, in

effect, makes the tube 19 dead as long as that current is passingthrough the resistance 18.

When the knob 45, or any other tuning knob,

is lifted to break the current through its variable resistance such as58, the current ceases through the resistance 10, and, as a result, thetube 19 is no longer dead because electrons flow from the cathode 89 tothe plate 82, causing a current through a conductor 83 which includes aresistance 84 (found satisfactory if approximately the same asresistance 59). The resistance 84 is connected to a wiper arm of avariable resistance 85 which is in series with the resistance 59. The

resistance 85 has been found satisfactory if three million ohms.

These connections cause a suitable current to be maintained in the tubesH and I2, even though no current passes through the variable resistors59 and 53 for the following reasons:

When tubes II and i2 are normally operated by tube 52, there is alwayseither no current 01'' maximum current flow in the respective tubes asthe case may be, since the grids have either no 55 bias or bias be ondcut-off, which means motor will run in either one or'the other directiondepending upon which of the two tubes has the normal current fiow. Butwhen tube 19 controls II and I2 through resistances 84 and 85, a state 0in between cut-ofi bias and no bias is obtained wherein current willflow in tube H but not to the extent of completely stopping fiow in tubel2 by a high negative bias. In short, a state is reached whereby anequal current flows in each tube and thus buck one another in thearmature with the result that the latter stands still. The fineadjustment required is obtained by virtue of the fact that resistor is afractional part of the total state resistor 84 and thus has but a 7correspondingly small portion of the total plate and 85. This means thatafter adjustment of resistance 85 has been made, the same smallpotential bias is always impresed on grid of l I thus rendering thisalways at the half operation point. The tube 19, therefore, makes itpossible to provide any number of tuning knobs 45 and 46 each having anormally idle variable resistor 50 and wiper arm 49.

It is possible to utilize the remote tuning lead conductor 28 for remotevolume control. To effect this a. conductor 86 leads from the conductor28 to a remote tuning handle shown as a wiper arm 81 running over a highresistance 88 forming a continuation of the conductor 86. To change thevolume of sound the wiper arm 81 is shifted on the resistance '88 so asto alter the voltage on a screen grid 89 forming part of a radiofrequency amplification tube 90 in the radio set, thus altering volumeof sound.

It is possible to attach a loud speaker on to the remote tuning leadconductors 28 and i6, provided these are of sufficient gage to carry thenecessary current. The loud speakers terminals 9i and 92 are shown asconnected through condensers 93 and 94. To block high voltagealternating currents a choke coil 95 may be needed. The choke coil isshown in the conductor I6, between the loud speaker terminals and thegrid 5i. The loud speaker unit shown at 96 connects through condensers97, and 98 to the leads l6 and 28.

What was said above about driving the motor in one direction applies todriving it in the opposite direction with altered voltages on the grids.58 and 65, and this is true whether the polarity of the armature or ofthe fields is what is altered. When the variable resistance 50 re--mains unaltered, the grids 58 and 65 balance opposing tendencies todrive the armature. In the form shown the motor is supposed to havefields of constant polarity. They may even be permanent magnets.

The armature in the device shown was wound with 44 gage enamelled coppedwire to about 1500 ohms. The rotary armature used was a lap wound withback pitch of 5 and a front pitch of 3, having seven poles or armaturewinding elements. The motor was about the size used in toy electrictrains.

Instead of the priming device described above, a switch 99 in the main29 or 39 may be used.

It will be found useful to provide shields for at least some of thetubes of a common type.

Having thus described certain embodiments of the invention, what isclaimed is."

1. A driving device including a motor having a field and an armature, apair of electron vacuum tubes with grids and having plates providingcurrents adapted to move the armature relatively to the field inopposite directions, a connection to the grid of one tube from the plateof the other tube to control the current therein, a control device, anda connection from the grid of the other tube to the control device.

2. A driving device including a motor having a field and an armaturerotatable relatively to the field, a pair of electron vacuum tubes withgrids and having plates providing currents adapted to rotate thearmature in opposite directions, a connection to the grid of one tubefrom the plate of the other tube to control the current therein, avoltage control device, and a connection from the grid of the other tubeto the control device.

3. A power device having a motor including coils with a resistance ofhundreds of ohms, a

pair of electron tubes adapted to drive the motor in either directionthrough the coils, one of said tubes controlling the second, a variableresistance settable to control the first tube, and another electron tubeadapte'd to cause the pair of tubes to hold the motor idle when thecircuit is broken at the variable resistance.

4. In a control device a rotatable motor armature, a pair of leads tocarry current to the armature, an electron tube having a plate connectedto supply current to one lead, a grid for the tube, control means forits grid, a second electron tube having a cathode to supply current tothe same lead, a grid in the second tube directly coupled to the plateof the first tube, a bias resistor forming the connection between thecoupling and the lead, and a connection between the cathode of the firsttube and the plate of the second tube, means for maintaining a drop ofpotential along the connection, and a conductor from vthe second lead toan intermediate point of said connection.

ERIK B. HANSELL.

